Visual cosmetic inspection is commonly used for quality control, data acquisition, and data analysis. This is an important commercial function, which may be used for example, for visually distinguishing between flawed and flawless product from production/manufacturing/assembly processes of 3C industry.
A conventional approach is to analyse product samples, surface by surface, which eventually takes long time. Given a certain throughput rate of any given production process, only a small number of samples can be inspected. In other words, some defective products may be identified as flawless without inspection and reaches the end of the production line. Therefore, the operator has to make a compromise between the production rate and the product quality rate. For example, a visual cosmetic inspection apparatus is disclosed in Patent US 20080239301 A1 for performing visual inspection of an object form a multiple of perspectives, which uses observation optical system, a first mirror and two second mirrors. By rotating the first mirror while moving it integrally with the observation optical system, observation of the side surface of the object, such as a wafer. Besides, the views of a top surface and bottom surface may be obtained by moving and rotating the first mirror and the two second mirrors integrally with the observation optical system. Therefore, a period of the inspection cycle time has to be set long enough to allow the completion of the repositioning of the mirrors for a multi-perspective inspection, which decreases the inspection rate.